The present invention relates to an ink jet printing apparatus. In such an apparatus, pressure oscillation is applied to ink in an ejection head by an electrostrictive vibrator thereby causing a jet of ink to be ejected from the head. The jet separates into droplets which are charged and electrostatically deflected onto a copy sheet where it is desired to print a dot. Where it is not desired to print a dot, the droplets are not charged and hit a gutter. Orthogonal scanning movement is effected between the head and sheet.
A problem which has remained heretofore unsolved in such an apparatus is that the amount of deflection of the ink droplets varies in accordance with the ink temperature and the position of the printed dot on the sheet accordingly varies. Although various expedients have been proposed to overcome this problem, a completely satisfactory solution has not been discovered heretofore.